South Slough, Coos Bay

South Slough, Coos Bay

by | May 24, 2023

South Slough is a tidal embayment designated as a National Estuarine Research Reserve that extends 6 miles (10 km) south from Coos Bay, which is an estuary of the Coos River, about 13 miles (21 km) north-northeast of Bandon and 4 miles (6.5 km) south of Charleston, Oregon. The reserve was established in 1974 and has an interpretative center about 4 miles (6.4 km) south of Charleston on Seven Devils Road. The Coos Bay estuary has extensive wetlands and tidal flats such as those in South Slough where the underlying bedrock is sandstone of the Empire Formation that developed during the Miocene. These rocks are covered by marine terrace deposits that accumulated during the Pleistocene and have since been tectonically uplifted in association with the adjacent Cascadia subduction zone. Terrace sediments consist largely of fine material such as clay, silt, and fine sand that were originally deposited in protected marine environments. Interbedded with terrace sediments are layers of peat which represent buried marshes or forests. Some of the most extensive and best-preserved marine terraces along the southern Oregon coast are at South Slough and include the Metcalf and Seven Devils terraces. Geochronological studies of these terraces have used fossils of corals, bryozoans, mollusks, and urchins associated with the marine sediments to estimate the rate of uplift, and the data suggests rates of about 3 feet (1 m) every 1,000 years, which has contributed to the creation of the expansive wetlands of South Slough.

Coos Bay is part of the traditional territory of the Coos people who are closely related to the Lower Umpqua and Siuslaw peoples. In about 500 AD, the Miluk Coos began to inhabit Coos Bay and they subsisted on deer, elk, seafood, berries, seaweed, and edible plants and roots, and their shell middens and fish traps are still present along shorelines. There were about 40 settlements and camps in the Coos Bay area and each village had a headman and was independent from other villages. Seasonal camps were used to fish for salmon and Pacific lamprey, and many of the fish were dried and stored for winter. Red cedar was used to build plank houses and canoes, and the bark was used to make baskets for carrying and storing food. Regular contact with Europeans started in the late 1700s when trading materials were introduced, and foreign diseases started to decimate small villages. In 1836, Hudson’s Bay Company established a trading post called Fort Umpqua about 45 miles (72 km) northeast of South Slough on the Umpqua River and many Coos, Lower Umpqua, and Siuslaw people traded beaver furs and hides for manufactured goods. In 1850, Congress passed the Oregon Donation Land Act, which provided 320 acres of free land to each man and woman over the age of eighteen who had settled in the territory prior to 1850, or 160 acres if they had arrived after 1850. In 1853, the Coos Bay Commercial Company was formed to promote white settlement of the area, and by 1854, Euro-American settlers were claiming lands along the margins of Coos Bay. In 1855, Indian Agent Joel Palmer held meetings with the Coos people to negotiate a treaty that eventually led to the creation of the Siletz Reservation as part of an exchange for the cessions of nearly 1.9 million acres of land that reached as far east as the Coast Range.

South Slough is the southernmost drainage basin in the Coos Bay watershed and is fed mostly by Winchester Creek that drains about 19,300 acres (7,810 ha) of public and private timberlands, protected forests, coastal streams and riparian areas, saltmarshes, estuarine mudflats, and tidal channels. The streams and tidal wetlands of South Slough have been degraded due to industrial development and historical management practices on public and private lands. The cumulative effects of cutting streamside forests, inadequate riparian buffer areas, removal of woody debris from channel, and road construction, have contributed to increased streamflow and sediment redistribution on enormous scales. These activities have decimated populations of anadromous fishes, and greatly diminished critical habitat for resident and migratory shorebirds. South Slough National Estuarine Research Reserve was the first reserve designated by the Coastal Zone Management Act of 1972. In 1974, Oregon was awarded federal funds for the initial land acquisition and management of the reserve, and by 1991, the land within the original proposed administrative boundaries of the reserve had been acquired and now comprises 4,800 acres (1,942 ha) running north-south along Winchester Creek. Read more here and here. Explore more of South Slough and Coos Bay here:

About the background graphic

This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2022 (bottom). Each stripe represents the average global temperature for one year. The average temperature from 1971-2000 is set as the boundary between blue and red. The color scale goes from -0.7°C to +0.7°C. The data are from the UK Met Office HadCRUT4.6 dataset. 

Credit: Professor Ed Hawkins (University of Reading). Click here for more information about the #warmingstripes.

Please report any errors here